Objective: To determine the effects of weaning age on postweaning belly-nosing
behavior and umbilical lesions in a commercial multi-site production system
environment.

Materials and methods: This study was conducted as a randomized complete
block design. Treatments were weaning at 12, 15, 18, and 21 days of age (N
= 2272 pigs). Each block was an off-site nursery, with four replicates (pens)
of each treatment in each of four blocks. All pigs in a block were weaned from
a 7300-head sow farm on the same day (Day 0). Each pen was observed for 15
minutes on Days 7, 14, and 21. Pigs demonstrating sustained belly-nosing behavior
(>= 10 seconds) were recorded. After the observations on Day 21, the umbilical
region of each pig was examined and scored for lesions associated with belly
nosing. A repeated measures mixed model with linear and quadratic contrasts
was used to test the effects of weaning age on belly-nosing prevalence, percentage
of pigs classified as "nosers," umbilical lesion scores, and percentage
of pigs with umbilical lesions at Day 21, with pen the experimental unit in
all analyses.

Results: Belly-nosing behavior and umbilical lesions were less frequent
(quadratic, P < .05) as weaning age increased. Although the incidence
of belly-nosing behavior gradually decreased as weaning age increased to 21
days, nosing activity and umbilical lesion scores nearly doubled as weaning
age decreased from 15 to 12 days of age.

Implications: Weaning pigs at less than 15 days of age significantly
increases belly-nosing behavior and associated umbilical lesions.